The present invention relates to a copper alloy sputtering target and a method for manufacturing the same, and particularly relates to a sputtering target suitable for forming a thin film made of a copper alloy for use as a wiring in a semiconductor integrated circuit, and a method for manufacturing such a sputtering target.
Conventionally, while Al (specific resistance of roughly 3.1 μΩ·cm) has been used as the wiring material for semiconductor integrated circuits, pursuant to the refinement of wirings, Cu (specific resistance of roughly 1.7 μΩ·cm) with lower resistance has been put into practical application. As the process for forming a copper wiring, generally adopted is the method of forming a diffusion barrier layer made of Ta or TaN on a wiring layer or a wiring groove, and thereafter electroplating the copper. As the underlayer (seed layer) for performing the electroplating, copper or copper alloy is generally subject to sputter deposition.
Nevertheless, in case of forming a fine wiring of which width is 0.130 nm or less; for instance, 90 nm, 65 nm, 45 nm, or 20 nm, the seed layer will be an ultra-thin film of which thickness is less than the wiring width, but when forming such an ultra-thin seed layer, there is a problem in that a favorable seed layer cannot be formed due to the particles that are generated during sputtering. The formation of the seed layer is of importance, but defects such as disconnections are to be formed if particles exist in the seed layer.
The present applicant has previously proposed inventions related to high-purity copper or copper alloy sputtering targets for forming the wiring of semiconductor integrated circuits (refer to Patent Documents 1 to 3). While these inventions can prevent the generation of defects such as voids, hillocks and disconnections, yield low specific resistance, and offer EM resistance properties and oxidation resistance properties, the generation of particles caused by trace amounts of impurities in recent ultra-fine wirings is now regarded as a problem. Note that, while not directly related to the present application, Patent Documents 4 to 6 disclose methods for producing high-purity copper.